The present invention relates to an aircraft engine and, in particular, to an aircraft engine capable of purifying the exhaust gas as needed according to the engine operating condition.
The exhaust gas from vehicles contributes to air pollution, and the permissible concentration values of air pollutants, such as hydrocarbon (CO) and nitrogen oxides (NOx) contained in the exhaust gas have been controlled by laws and regulations. To comply with these laws and regulations, exhaust gas purifying devices are mounted in vehicle engines.
Like vehicles, aircraft emit exhaust gas from their engines. However, this exhaust gas is under no legal control. Since the exhaust gas from aircraft at the time of preparing for takeoff and landing contributes to air pollution in the neighborhood of the airport, it is desirable that the exhaust gas from aircraft be purified like the exhaust gas from vehicles.
However, in aircraft, it is essential that a desired speed and altitude can be ensured in the air, and aircraft should be able to output a desired engine power. Providing an aircraft engine with an exhaust gas purifying device results in a reduction in engine power. Thus, no measures have been taken to purify the exhaust gas from aircraft engines.
It is accordingly an object of the present invention to provide an aircraft engine which is capable of purifying the exhaust gas to thereby mitigate air pollution in the neighborhood of an airport and which can provide a desired engine power during flight.
Another object of the present invention is to provide an aircraft engine which involves no increase in aircraft weight and does not affect the flight condition and which is capable of mitigating air pollution in the neighborhood of an airport.
Still another object of the present invention is to provide an aircraft engine in which an engine control mechanism is appropriately controlled on the basis of information from a detection means for detecting the aircraft condition to thereby reduce the amount of pollutant in the exhaust gas and which is capable of providing a maximum engine output as needed.
To achieve the above objects, according to a first aspect of the present invention, there is provided an aircraft engine comprising an exhaust gas purifying device for purifying exhaust gas from the engine, and a switching means for switching the engine between an emission-emphasized mode in which the exhaust gas from the engine is purified by the exhaust gas purifying device and an output-emphasized mode in which emphasis is placed on engine output.
Thus, in the aircraft engine of the present invention, when the emission-emphasized mode is selected by the switching means, the exhaust gas from the engine is purified by the exhaust gas purifying device. When the output-emphasized mode is selected by the switching means, emphasis is placed on the engine output, and the engine is operated so that a maximum output can be achieved.
As a result, an aircraft engine is provided which can purify the exhaust gas from the engine to thereby prevent air pollution and which is capable of ensuring a desired engine output as needed.
According to a second aspect of the present invention, the switching means is controlled on the basis of detection results obtained by a detecting means for detecting whether the aircraft is in a pre-takeoff/post-landing state or a flight state. When the aircraft is in the pre-takeoff/post-landing state, the engine is operated in the emission-emphasized mode, and when the aircraft is in the flight state, the engine is operated in the output-emphasized mode.
Thus, according to the second aspect of the present invention, the detecting means detects the state of the aircraft, that is, detects whether the aircraft is in the pre-takeoff/post-landing state or the flight state to control the operation of the switching means.
Thus, according to the second aspect of the present invention, when the aircraft is in the pre-takeoff/post-landing state, the engine is operated in the emission-emphasized mode, and when the aircraft is in the flight state, the engine is operated in the output-emphasized mode.
According to a third aspect of the invention, the detecting means detects whether the aircraft is at rest on the ground with the engine operating, or the aircraft is moving on the ground at low speed, or the aircraft is flying. When the detecting means detects that the aircraft is at rest on the ground with the engine operating, or it is moving on the ground at low speed, the engine is operated in the emission-emphasized mode. When the detecting means detects that the aircraft is flying, the engine operation is switched to the output-emphasized mode.
Thus, in the third aspect of the present invention, the detecting means detects whether the aircraft is at rest on the ground, with the engine running at idle, or it is moving at, for example, an airport to a predetermined runway, that is, performing so-called taxying, or it is flying. When the aircraft is at rest on the ground, with the engine running at idle, or it is moving at, for example, an airport to a predetermined runway, that is, performing so-called taxying, the engine is operated in the emission-emphasized mode. When the detecting means detects that the aircraft is flying, the engine is operated in the output-emphasized mode.
Thus, according to the third aspect of the present invention, when no great engine power is required and it is necessary to prevent air pollution in the neighborhood as in the case in which the aircraft is at rest on the ground, with the engine running at idle, or performing taxying or the like, the switching means is controlled on the basis of the detection results obtained by the detecting means so as to operate the engine in the emission-emphasized mode.
On the other hand, when a predetermined great engine output is required as in the case in which the aircraft is starting to fly and taxying, or rising to a predetermined altitude, or cruising at the predetermined altitude or the like, the detecting means detects it, and controls the switching means accordingly so that the engine may be operated in the output-emphasized mode. Thus, it is possible to obtain a desired great engine output whenever it is required, so that the flight is not adversely affected.
According to a fourth aspect of the present invention, the exhaust gas purifying device is provided so as to be branched off from a first exhaust passage for discharging the exhaust gas to the exterior of the aircraft, and has a second exhaust passage for discharging the exhaust gas to the exterior of the aircraft and an exhaust purifying catalyst provided in the second exhaust passage.
Thus, in the fourth aspect of the present invention, when the engine exhaust gas is purified in the emission-emphasized mode, the exhaust gas flows into the second exhaust passage to be purified by the exhaust purifying catalyst before it is discharged to the exterior of the aircraft.
As a result, in the fourth aspect of the present invention, the exhaust gas discharged from the aircraft engine is purified by the exhaust purifying catalyst provided in the exhaust passage.
According to a fifth aspect of the present invention, the switching means is provided at the branch point between the first exhaust passage for discharging the exhaust gas to the exterior of the aircraft and the second exhaust passage having the exhaust purifying catalyst and adapted to discharge the exhaust gas after purifying it, and is formed by an exhaust passage switching means capable of introducing the exhaust from the engine into the first exhaust passage or the second exhaust passage.
Thus, in the fifth aspect of the present invention, the switching means is operation-controlled to change its position on the basis of the detection result obtained by the detecting means, thereby causing the exhaust gas from the engine to flow into the first exhaust passage or the second exhaust passage.
As a result, in the fifth aspect of the present invention, in the emission-emphasized mode, the exhaust from the engine is introduced into the second exhaust passage by the switching means, and the exhaust gas is purified by the exhaust purifying catalyst provided in the second exhaust passage. In the output-emphasized mode, the exhaust from the engine is introduced into the first exhaust passage, and the exhaust gas is discharged without being purified.
According to a sixth aspect of the present invention, the detecting means is provided outside the aircraft and formed by a wing-like member adapted to be operated by an airflow from the front side of the aircraft.
Thus, in the sixth aspect of the present invention, when the aircraft is running on the ground at a predetermined speed, or flying, it receives an airflow of a predetermined pressure, whereby the detecting means formed by a wing-like member is driven to control the operation of the switching means. On the other hand, when the aircraft is at rest on the ground or taxying at low speed, it does not receive the airflow of a predetermined pressure, so that the detecting means formed by a wing-like member is not driven, and controls the switching means accordingly.
According to a seventh aspect of the present invention, the exhaust flow passage switching means is driven by the wing-like member, and when the aircraft is in the pre-takeoff or post-landing state, the wing-like member does not operate and the emission-emphasized mode is selected, the exhaust flow passage switching means being arranged at the branching point so as to be capable of introducing the exhaust gas into the first exhaust passage; when the aircraft is in the flight state, the output-emphasized mode is selected and the wing-like member is operated by lift to drive the exhaust flow passage switching means, the exhaust flow-passage switching means being arranged at the branching point so as to be capable of introducing the exhaust gas into the second exhaust passage.
Thus, in the seventh aspect of the present invention, when aircraft is in the pre-takeoff or post-landing state, the wing-like member receives no airflow at a predetermined pressure so that it does not operate, the exhaust gas being introduced into the first exhaust passage. On the other hand, when the aircraft is in the flight state, the wing-like member is operated by lift generated to drive the exhaust flow passage switching means, thereby introducing the exhaust gas into the second exhaust passage. Since the exhaust purifying catalyst is provided in the second exhaust passage, the exhaust gas is purified before it is discharged during flight.
As a result, in the seventh aspect of the present invention, the exhaust flow passage switching means is driven by the wing-like member, so that when the aircraft is at rest on the ground or taxying at low speed, the emission-emphasized mode is selected, and the exhaust gas is introduced into the second exhaust passage to be purified. When the aircraft is running on the ground at a predetermined speed or flying, the output-emphasized mode is selected and the exhaust gas is introduced into the first exhaust passage to be discharged without being purified.
According to an eighth aspect of the present invention, the switching means is provided with an intake air heating device and an intake air throttle valve, and there is provided an intake air flow passage switching means capable of switching between an intake air passage for supplying intake air to the engine main body by way of the intake air heating device and an intake air passage for supplying intake air to the engine main body without passing it through the intake air heating device and the intake air throttle valve.
Thus, in the eighth aspect of the present invention, an intake air heating device is provided in one intake air passage, so that when intake air is supplied into this intake air passage when the temperature is low or in a cold state, the intake air is heated to undergo temperature rise, thereby preventing generation of white smoke and reducing the amount of THC discharged. Further, since an intake air throttle value is provided, the intake air amount is appropriately adjusted, and it is possible to control the amount of exhaust gas recirculated by an exhaust gas recirculating device (EGR).
As a result, in the emission-emphasized mode, the operation of the intake air flow passage switching means is controlled to supply intake air to the intake air passage where the intake air heating device is provided, thereby reducing the amount of air pollutant in the exhaust gas. Further, the intake air amount is appropriately controlled by the intake air throttle valve, and it is possible to reduce the generation of NOx (nitrogen oxides) by means of the exhaust gas recirculating device (EGR).
In the output-emphasized mode, the operation of the intake air flow passage switching means is controlled to introduce intake air into the intake air passage where no intake air heating device is provided, and intake air is directly supplied to the engine main body without passing it through the intake air heating device and the intake air throttle valve, whereby the intake resistance of the intake air is reduced, and it is possible to obtain an appropriate engine power output and to achieve an improvement in fuel efficiency.
According to a ninth aspect of the present invention, the exhaust gas purifying device is provided in the intake air passage for supplying intake air to the engine main body, and is formed by the intake air heating device capable of raising the temprature of the intake air.
Thus, in the ninth aspect of the present invention, the intake air heating device is provided in the intake air passage leading to the engine main body, so that when intake air is supplied to this intake air passage at low temperature or in a cold state, the intake air is heated to undergo temperature rise, thereby preventing generation of white smoke and reducing the amount of THC discharged. Thus, in the case of the emission-emphasized mode, the air pollutant in the exhaust gas is removed.
According to a tenth aspect of the present invention, the engine is formed by a diesel engine, and the exhaust gas purifying device is formed by a glow plug for heating an engine combustion chamber.
Thus, in the tenth aspect of the present invention, in the emission-emphasized mode, the glow plug assists in igniting the diesel engine, so that at low temperature or in a cold state, generation of white smoke at the engine start is prevented, whereby the amount of THC discharged is reduced and it is possible to achieve an improvement in fuel economy.
According to an eleventh aspect of the present invention, the exhaust gas purifying device is formed by a fuel injection control mechanism capable of controlling the fuel injection state so as to reduce the discharge amount of air pollutant in the exhaust gas.
Thus, in the eleventh aspect of the present invention, in the emission-emphasized mode, the fuel injection control mechanism controls fuel injection amount, fuel injection timing (including injection during exhaust stroke or the like), fuel injection pattern (injection ratio control in pilot injection, two-stage injection, delta-type injection or the like) so as to reduce the air pollutant in the exhaust gas, and the discharge amount of THC, CO, NOx, SPM, smoke, CO2 or the like in the exhaust gas is reduced through optimum fuel injection and combustion.
On the other hand, in the output-emphasized mode, the fuel injection control mechanism controls fuel injection amount, fuel injection timing (including injection during exhaust stroke or the like), fuel injection pattern (injection ratio control in rectangular injection, pilot injection, two-stage injection, delta-type injection or the like) so as to obtain maximum engine output.
According to a twelfth aspect of the present invention, the exhaust gas purifying device is formed by a suction/exhaust valve control mechanism capable of controlling the valve timing to change so as to reduce the discharge amount of air pollutant in the exhaust gas.
Thus, in the twelfth aspect of the present invention, the suction/exhaust valve control mechanism is capable of setting an optimum valve timing according to the operating condition. In the emission-emphasized mode, the suction/exhaust valve control mechanism controls to change the valve timing so as to make it possible to reduce the discharge amount of air pollutant in the exhaust gas. At low temperature or in a cold state, it delays the opening of the intake air valve to raise the intake air temperature in the cylinder to prevent generation of white smoke. When the engine is running at idle or at low speed, it advances the closing of the intake air valve to prevent blow-by of the gas, and, by increasing the real compression ratio, prevents white smoke, reduces the discharge amount of THC, achieves an improvement in fuel consumption ratio, etc., whereby the discharge amount of air pollutant in the exhaust gas is reduced.
Further, in the output-emphasized mode, the suction/exhaust valve control mechanism appropriately controls the valve timing so that a maximum engine output may be obtained, and, when the engine is running at high speed, it delays the closing of the intake air valve to thereby increase the volumetric efficiency, making it possible to obtain maximum output.
According to a thirteenth aspect of the present invention, the exhaust gas purifying device is formed by an ignition control mechanism capable of changing the ignition period so that the discharge amount of air pollutant in the exhaust gas may be reduced.
Thus, in the thirteenth aspect of the present invention, in the emission-emphasized mode, the ignition control mechanism controls the ignition timing of the ignition device to realize an optimum ignition period, thereby reducing the discharge amount of air pollutant in the exhaust gas.
Further, in the output-emphasized mode, the ignition control mechanism appropriately realizes an ignition period which allows a maximum engine output to be obtained.
According to a fourteenth aspect of the present invention, the exhaust gas purifying device is formed by an exhaust gas recirculating device which recirculates the exhaust gas to use it as intake air.
Thus, in the fourteenth aspect of the present invention, in the emission-emphasized mode, the exhaust gas is recirculated by the exhaust gas recirculating device and supplied again to the cylinder with air-fuel mixture. As a result, the temperature in the combustion chamber decreases, and the generation of NOx is reduced.
According to a fifteenth aspect of the present invention, the exhaust gas recirculating device has an exhaust gas recirculating valve.
Thus, in the fifteenth aspect of the present invention, the exhaust gas recirculating device has an exhaust gas recirculating valve, so that it adjusts the amount of gas recirculated to achieve an optimum EGR ratio for each operating condition, thereby reducing the discharge amount of NOx, THC, CO, SPM, etc.
According to a sixteen aspect of the present invention, the exhaust gas recirculating device is provided with an exhaust gas recirculating cooler.
Thus, in the sixteen aspect of the present invention, the exhaust gas recirculating cooler cools the exhaust gas used for the recirculation of the exhaust gas, and lowers the maximum combustion temperature at the time of combustion, thereby reducing the discharge amount of NOx.
According to a seventeenth aspect of the present invention, in the exhaust gas recirculating device, the amount of exhaust gas recirculated is controlled by the intake air throttle valve.
Thus, in the seventeenth aspect of the present invention, the intake air amount is adjusted by the intake air throttle valve, and the amount of exhaust gas recirculated by the exhaust gas recirculating device (EGR) is appropriately controlled.
According to an eighteenth aspect of the present invention, the exhaust gas purifying device is formed by an exhaust throttle valve which is provided in the second exhaust passage and is capable of reducing the discharge amount of air pollutant.
Thus, in the eighteenth aspect of the present invention, in the emission-emphasized mode, the back pressure of exhaust gas is increased to control the exhaust gas recirculation ratio, and the engine load is increased to improve the warming-up property and prevent generation of white smoke.
According to a nineteenth aspect of the present invention, the exhaust gas purifying device is formed by an exhaust filter which is provided in the second exhaust passage and is capable of reducing the discharge amount of air pollutant.
When the engine is a diesel engine, an SPM removal filter is adopted as the exhaust filter. Thus, in the nineteenth aspect of the present invention, in the emission-emphasized mode, it is possible to achieve a reduction in SPM (particulate substance) peculiar to the exhaust gas from a diesel engine.